I. Field of the Invention
This invention relate to devices for conducting assay methods. The ability to employ receptors directed to specific compounds in assaying for the presence of a compound of interest has created a burgeoning diagnostic assay business. Over the years, numerous simplified test systems have been developed for the rapid detection of materials of interest in biological and industrial fluids. These systems or devices in their simplest form usually involve the combination of a test reagent specifically reactable with the material of interest to give a visual response and a carrier for the test reagent. Bibulous paper is the most commonly used material for the carrier. A portion of the carrier is usually impregnated or coated with one or more of the test reagents. The portion of the carrier containing the test reagents is brought into contact with the sample containing the material of interest. The contact may be accomplished by immersing the portion of the carrier with the test reagents into the sample in an aqueous medium or an aqueous sample can be allowed to traverse a bibulous carrier by capillary migration through the portion of the carrier containing the test reagent. The test zone may be first created on the carrier or the zone may be produced during the running of the assay.
A concentrating zone method in heterogeneous assays has found broad application. The method employs a device that has an immunosorbing zone to which a specific binding pair member is fixed non-diffusively. The immunosorbing zone serves as an entry for the sample and reagent solutions. In liquid receiving relationship, either directly or indirectly with the immonosorbing zone, is a liquid absorbing zone which serves to draw liquid through the immunosorbing zone, store liquid and may serve to control the rate at which the liquid is drawn through the immunosorbing zone. Employed in the method in conjunction with the device is a signal producing system which has a signal label member conjugated to a specific binding pair member. The immunosorbing zone may include one or more members of the signal producing system which are bound to the zone in a manner to permit or inhibit diffusive movement of the signal producing system component. In accordance with the method protocol, the amount of signal label bound in the detection zone in the immunosorbing zone is related to the amount of the material of interest in the sample. In the method the assay device is contacted with liquid sample to which may have been added one or more components of the signal producing system. The device may subsequently be contacted with one or more solutions which contain remaining components of the signal producing system and serve to wash the immunosorbing zone free of non-specifically bound signal label. The signal producing system provides for a detectible signal in the immunosorbing zone which can be compared to a signal level based on a standard having a known amount of analyte.
The concentrating zone method technology has been applied in a number of commercial products, such as, for example, the ICON.RTM. device (Hybritech Corporation), the TESTPACK.TM. device (Abbott Laboratories), and the SUDS.TM. device (Murex Corporation).
A chromotographic technique for carrying out qualitative and/or quantitative assays for an analyte are also known. The assay involves contacting a portion of a bibulous material with a liquid medium containing the analyte and optionally other members of a signal producing system, which includes a labeled specific binding pair member. The bibulous material usually contains one or more zones for specifically binding the analyte. The bibulous material may also contain one or more members of a signal producing system. The liquid medium is allowed to traverse the bibulous material by capillary action and the bibulous material is contacted with remaining members of the signal producing system. The presence of analyte in a sample can be determined by examining the bibulous material for a signal in each of the zones and the quantity of analyte can be determined by relating the position of a border between signal and no signal in any one zone to the amount of analyte in the sample or counting the number of zones having or not having a signal and relating the number of zones to the amount of analyte in the sample. Exemplary of an immunochromotographic technique in accordance with the first approach above is the Acculevel.TM. product sold by Syva Company.
It is desirable to provide an immunoassay with the broad application of a heterogeneous assay which is also simple, rapid, accurate, and safe for unskilled persons to perform in environments outside of sophisticated laboratory settings. It is also desirable to provide a diagnostic device for conducting such assays wherein all of the reagents are contained and it is left only to add the sample to be tested to the device. Such a device would be convenient and eliminate the need for critical addition steps.
2. Description of the Related Art
A concentrating zone method in heterogeneous immunoassays is described in U.S. Pat. No. 4,366,241. A test device for detecting low concentrations of substances in fluids is described in U.S. Pat. No. 3,811,840. An improved heterogeneous immunoassay method and assembly is discussed in European Application Publication No. 0 141 547. U.S. Pat. No. 4,517,288 discloses a solid phase system for ligand assay. An integrated material for chemical analysis and a method of using the same is discussed in U.S. Pat. No. 4,270,920. The performance of routine chemical reactions in compartmentalized containers is described in U.S. Pat. No. 3,825,410. An immunodiffusion plate apparatus is described in U.S. Pat. No. 3,645,687. The performance of chemical or biological reactions within an absorbent matrix pad is discussed in U.S. Pat. No. 3,888,629. A test device for assaying liquid samples for the presence of a predetermined reagent is described in U.S. Pat. No. 4,246,339. An immobilized antibody or antigen for immunoassay is disclosed in U.S. Pat. No. 4,407,943. U.S. Pat. No. 3,915,647 discloses a device for determining the concentration of a substance in a fluid. U.S. Pat. No. 4,632,901 describes a method and apparatus for immuno-assays.